1. Field of the Invention
The present invention relates to a printer apparatus which performs printing in accordance with the printing pattern stored in a frame memory, and more particularly to a printer apparatus which produces satisfactory print even if part of a printing pattern is often changed
2. Description of the Related Art
Various kinds of labels are used in the business of administering the manufacturing process, ordering, stock, sales, etc. In many cases, the article information needed for the administration is represented by characters and bar codes printed on a label, and this label is adhered to the corresponding article. Since the bar code on the label can be easily read by an optical reader, the use of such a bar code is advantageous in the automation or rationalization in the business of administration. FIG. 1 shows an example of an administration label, such as that mentioned above. The label shown in FIG. 1 is divided into a plurality of regions by ruled lines. Titles, such as "Receiver", "Part No.", "Serial No.", "Date", etc. and the article information corresponding to these titles are printed in the respective divided regions. On the label, the article information and its title are expressed as a string of characters including numerals and symbols, but part of the article information is expressed as a bar code. Incidentally, the characters used for indicating the title are smaller than those used for indicating the article information.
A conventional printer apparatus used for printing data on such an administration label will be described. The conventional printer apparatus comprises: a frame memory for storing the printing pattern for one label; a printing head driven in accordance with the printing pattern stored in the frame memory; and a processing circuit for producing a printing pattern in the frame memory in accordance with a plurality of pieces of printing data (e.g., a ruled line, a title, and article information) supplied from an external host computer. The processing circuit includes a font memory for storing various types of fonts (i.e., the fonts for the ruled lines, characters, bar codes, etc.). Each of the fonts is selected by a corresponding data included in the printing data and is read out of the font memory. To prepare a printing pattern, the readout font is developed in the frame memory, to thereby form a graphic pattern having a desirable size. This graphic pattern is expressed by use of a plurality of memory bits which are employed by the frame memory and arranged in a matrix pattern. All these memory bits are cleared to be "0" in logic level beforehand (the "0"-level memory bits correspond to a spa e portion where the printing head does not effect printing), and are selectively set to "1" in logic level to express the graphic pattern (the "1"-bit memory bits correspond to a dot portion where the printing head effects printing).
The character font uses a vector format for representing the outline of a character image within a font frame having a predetermined size. In general, it is desirable for the character font to be designed in such a way as to produce the largest possible character images while simultaneously leaving a certain margin along the font frame. If the character font is designed like this, the quality of print can be improved, and adjacent characters are prevented from being in contact with each other when they are printed. However, in the case where both an unornamented-character font and an ornamented-character font are stored in the font memory, the character image of the unornamented-character font is made to have the same size as the character image portion of the ornamented-character font (the character image portion being a portion obtained by excluding the ornamentation from the ornamented character). By so doing, a character of the unornamented-character font and a character of the ornamented-character font look satisfactorily balanced even if they are printed adjacent to each other on the label. As is seen from the graphic forms shown in FIG. 2, therefore, unornamented-character fonts F1-F4 produce an undesirably wide margin above their character images, while ornamented-character fonts F5 and F6 hardly produce a margin above their character image. The margin of the unornamented-character fonts is considerably enlarged when the fonts are developed in the frame memory.
Incidentally, article information is often changed in comparison with ruled lines or titles. In a conventional printer apparatus, therefore, that area of the frame memory which is determined by the attributes (namely, the frame size, the developing magnification, the developing start position, and the number of fonts) of the character fonts corresponding to the character string of the article information to be changed, is cleared. In this area of the frame memory, a character font corresponding to the character string which should replace the character string of the article information is developed. In the case where the character string of the article information is comprised only of unornamented characters and does not include any ornamented character, the developing magnification of these character fonts is sometimes set to be larger than in the case where the character string includes ornamented characters, so as to print the character string to have the largest possible size within the label region which is surrounded by the ruled lines, title, and bar code. If the character string of the article information is changed in the case where the developing magnification is set to be larger as above, the ruled lines, title and bar code may not be partly printed, as is shown in FIG. 3.
One method for solving this problem may be to replace the printing pattern in the frame memory with a new one and to effect printing on the basis of the new printing pattern. If this method is used, however, a long time is required for the preparations of printing, so that the printing on a label cannot be started at once. Another method for solving the problem may be to inhibit the developing magnification from being increased with respect to the character fonts which correspond to the character string of the article information including no ornamented characters. However, this alternative method restricts the flexibility in label layout, and it becomes impossible to make good use of the label region surrounded by the ruled lines, title, and bar code. The printing preparation time and the flexibility in label layout are important factors which the users consider when deciding to buy printer apparatuses. On the part of the manufacturers, therefore, it is necessary to provide a printer apparatus free from the problem noted above.